From the looks of it, your ex wasn’t ready with you initially but only came to realisation that he wanted you when he saw that you actually moved on from him...
He might have thought you wouldn’t have. He told you he wasn’t ready for a real relationship but you were, this suggests that both of you were not compatible enough to begin with. He even left you, you did not leave him.
In my opinion, I think you should move on with the new guy. Your ex, clearly, missed his chance with you at that opportunity.. there’s nothing he can do but deal with it.
That’s my take on it. The new guy you’ve met will probably feel very played and lead on. Don’t do that to him man.